1. Field of Invention
The invention relates to a flip-chip attach structure and a flip-chip attach method, and more particularly to a flip-chip attach structure and a flip-chip attach method for attaching a chip to a transparent substrate.
2. Related Art
In semiconductor package manufacturing processes, the flip-chip attach technology is widely used. The so-called flip-chip attach technology is, in brief, to form a plurality of protrusions on an active surface of a chip, and then to mount the chip on a substrate by the protrusions.
In general, the methods for attaching a chip to a substrate in a flip-chip manner are categorized into three kinds including a solder bump attach method, an anisotropic conductive adhesive film (ACF) attach method and a gold-to-gold pressing attach method. As shown in FIG. 1, the solder bump attach method is to form a solder bump 112 on a connecting pad 111 of a chip 11 in advance, and then the chip 11 is mounted on the substrate 12. As shown in FIG. 2 the ACF attach method is to form a gold bump 113 on a connecting pad 111 of a chip 11, and then an anisotropic conductive adhesive film 13 is used to adhere the chip to the substrate 12. As shown in FIG. 3, the gold-to-gold pressing attach method is to form a gold protrusion post 114 on a connecting pad 111 of a chip 11, and then the chip is mounted on the substrate 12 by way of direct pressing.
In the above-mentioned attach methods, the first and second methods are used frequently, wherein the first attach method is often used in the typical chip package processes while the second attach method is often used in the LCD manufacturing processes. In the LCD manufacturing processes, attaching the chip on the glass substrate are usually performed using the ACF attach method, and this technology is typically referred to as the COG (chip on glass) technology. The problem that the second attach method most frequently encounters is that the gold bump on the chip cannot completely contact the gold ball in the anisotropic conductive adhesive film, thereby reducing the product yield. In order to avoid this problem of the reduced yield, the areas of the connecting pad of the chip and the gold bump cannot be too small. This will limit the further shrinking of the chip area. In addition, because the anisotropic conductive adhesive film has to be adhered to the glass substrate, the transparent property of the glass substrate (transparent substrate) cannot be effectively utilized in some applications. In particular, it is inconvenient in the package application of the opto-electronic semiconductor chip.
Consequently, it is an important subject to provide a chip attach method capable of enhancing the connecting yield between the chip and the transparent substrate, optimized utilization of the transparent property of the transparent substrate, and reducing the area of the connecting pad on the chip.